1899, as a chemical term, short for gelatin and perhaps influenced by jell. The invention of this word is credited to Scottish chemist Thomas Graham (1805-1869). Hair-styling sense is from 1958. The verb meaning "to become a gel" is attested by 1902; figurative sense is from 1958. Related: Gelled; gelling.

gel

verb

To come to a firm and useful form; work: In this highly partisan county, it just didn't gel/ If this doesn't gel, the local people will be stuck/ Frost's saga fails to jell either as compelling drama or convincing social portraiture(1950s+)

(also jell out) To relax; chill out, kick back: After having five hours of class today I think I'll just go home and gel(1980s+ Students)

[second sense perhaps fr the notion of productively sitting still as a gelatin pudding does]

The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D.Copyright (C) 2007 by HarperCollins Publishers.Cite This Source